The broad objective of the proposed research is to determine whether influenza virus hybrids (recombinants) that might occur in nature, as a result of a mixed infection in an animal species, can be maintained in that or another species. It has been shown under experimental conditions that recombinant influenza viruses can be recovered from turkeys and pigs after exposure to antigenically distinct influenza A viruses. There is reason to suspect that new pandemic strains of influenza viruses may arise in this manner. The research will be directed toward the study of selected aspects of the pathogenesis of recombinant influenza virus infection in swine and turkeys which will include the following: 1) Determine the relative infectivity and pathogenicity of 6 recombinant viruses in the 2 host systems; 2) Determine intraspecies and interspecies transmissibility of 2 selected recombinants under simulated natural conditions; and 3) Determine the effect of "forced" transmission on the host and the virus.